DESCRIPTION: Applicant's Abstract Persons infected with the hepatitis B virus (HBV) or hepatitis C virus (HCV) are at high risk for serious long-term health problems, and they are potentially infectious to others. Because of the seriousness of these infections, the NIH has developed a national agenda for preventing the spread and consequences of HBV and HCV. This agenda includes early detection, treatment, and prevention efforts for high-risk and infected persons. Homelessness has reached crisis proportions in the US today. Recent research by our team and others suggests that homeless adults in urban areas are a group at particularly high risk for HBV and HCV infections due to high rates of risky drug use and risky sexual behaviors. Despite the apparent high risk, however, there is only limited research on viral hepatitis in this group. We propose to conduct epidemiologic and health services research regarding HBV and HCV in a population-based sample of 500 homeless adults. We will recruit a probability sample of homeless adults with oversampling of injection drug users from 30 shelters and meal programs in the Skid Row area of Los Angeles. Respondents will undergo a two-hour interview (including the Diagnostic Interview Schedule-DIS-IV) and blood draw for hepatitis serology. We will estimate the prevalence of HBV and HCV and identify risk factors for each. We will evaluate whether homeless adults with histories of injection and non-injection drug use, risky sex, serious alcohol or mental disorders, or chronic homelessness have an elevated risk for these infections. We will also conduct health services research in which we will describe the respondents' past history of HBV/HCV testing, awareness of infection status, medical care for HBV and HCV, and willingness to return for HBV/HCV test results. Further, we will identify utilization of medical and non-medical settings to identify sites for future screening, treatment, and prevention efforts. We will provide hepatitis B immunization to those that test negative for hepatitis B. We will bridge the gap between research and prevention by using the Theory of Planned Behavior to understand protective behaviors used by homeless adults to avoid exposure to infectious diseases.